In the field of optical communication, a system which outputs light beams with a plurality of wavelengths is used. For example, in the case of a system of outputting laser beams with two wavelengths, a configuration is adopted in which two semiconductor lasers manufactured for respective wavelengths are prepared and output light beams from the semiconductor lasers are mixed to be output (for example, refer to Patent Document 1).
In contrast, the inventor of this application proposes, as a two-wavelength laser light source configured without requiring such a complicated optical system, a semiconductor light emitting element capable of emitting laser beams with a plurality of wavelengths from a single chip by connecting a plurality of active layers with very different gain wavelengths in series and disposing a diffraction grating inside to realize independent oscillation of each wavelength (refer to Patent Document 2).